It has been generally recognized that an underlying cause of many learning disabilities is attributable to abnormal sensory integration and the capacity to receive, retain and correctly interpret visual information. Unfortunately, the determination of the exact nature of this disfunction has in many aspects been inconclusive and the diagnosis thereof somewhat difficult to discern. A dyslexic child, for example, typically exhibits an inability to comprehend one or more of the following: sound/symbol relationships, spelling, word patterns, sequences and combinations of letters. Although the problem had been considered as associated with emotional disturbances, biochemical imbalances, maturational lag, and brian lesions, recent studies pointed to a central malfunction in dyslexics, namely sequential disability and/or oculomotor malfunction. The results of such study were published by Dr. George Th. Pavlidis in a paper entitled Do Eye Movements Hold the Key to Dyslexia?, Dept. of Psychology, University of Manchester, Manchester, England (May 23, 1980). Testing methods were developed for measuring erratic eye movement patterns which were found to be characteristic of dyslexics during reading and nonreading sequential tasks. These prior tests, however, were primarily directed to the measurement and recording of very small or micro movements of the subject's eye and involved the use of photoelectric cell devices which were positioned in close proximity to the eye. A disadvantage of those early attempts for monitoring eye movement was that the minute or ultrafine ocular displacements did not provide sufficient information for analyzing the scanning eye movement which was of greater magnitude and occurred under actual reading conditions. Another shortcoming of those testing methods was that the resultant eye movement pattern was not juxtaposed over the visual stimuli so that eye movement could be tracked and recorded for determining the extent of the deviations in eye scanning patterns or other ocular motor malfunctions in response to specific stimuli.
Other prior art apparatus concerned with tracking eye movement utilized a separate light source for directing an incident ray at the viewer's eye and also employed a receiving camera for detecting the reflected light ray. A problem with the aforementioned system is that the incident ray presented a distraction--if not an annoyance--to the viewer, and the receiving camera which was positioned adjacent the viewer was similarly disconcerting.
Another drawback of the prior art reflected beam concept was that corneal aberrations were magnified in the reflected ray and thus did not present an accurate representation of the direction and magnitude of eye movement.
It should be further noted that the devices of the prior art were also primarily directed to detecting eye movement, whereas the instant invention provides a more comprehensive scanning approach.